Abstract: It is aimed to provide an optical head, an optical head manufacturing method and an optical disc device capable of correcting coma aberration generated due to different positions of emission points of a plurality of laser lights having different wavelengths. A two-wavelength laser light source 1 is arranged to correct coma aberration generated in a radial direction of a CD 80 in the case where an objective lens 6 is tilted to locate an inner peripheral end of the objective lens 6 in the radial direction of the CD 80 lower than an outer peripheral end thereof, and an objective lens actuator 9 tilts the objective lens 6 to locate the inner peripheral end of the objective lens 6 in the radial direction of the CD 80 lower than the outer peripheral end thereof.

Abstract: Described is an optical information medium measurement method of measuring a degree of modulation in an optical information medium of a multilayered structure having a plurality of information layers. The method includes measuring the modulation degree of each layer of the optical information medium, by use of a measurement optical system, obtaining a thickness between layers of the optical information medium, obtaining a reflectance of each layer of the optical information medium, and converting the measured modulation degree of each layer into a modulation degree at a reference optical system differing from the measurement optical system, based on a value indicative of the obtained thickness between layers and a value indicative of the obtained reflectance of each layer.

Abstract: An optical head includes a blue-violet laser light source for emitting a blue-violet laser beam, a mirror with a diffraction grating for transmitting and reflecting the blue-violet laser beam at a predetermined ratio, and a front monitor sensor for receiving transmitted light or reflected light from the mirror with a diffraction grating and creating an APC signal for controlling an output of the blue-violet laser light source. The mirror with a diffraction grating includes a first surface which the blue-violet laser beam enters, and a second surface facing the first surface. The first surface and the second surface are mutually parallel. A reflecting coat for transmitting and reflecting the blue-violet laser beam at a predetermined ratio is formed on the first surface, and a diffraction grating is formed on the second surface.

Abstract: An optical recording medium includes a cover layer, a plurality of recording surfaces, and a plurality of intermediate layers. The thicknesses of the layers are specifically determined and set at values which suppress a back focus problem. Because the optical recording medium suppresses back focus, the recording and reproducing of information using the optical recording medium is not obstructed.

Abstract: An optical recording medium (disk) capable of preventing a back focus at a face thereof and reducing the interference between beams reflected by each recording surface, thereby improving a quality of a servo signal and a reproductive signal. In a disk having (N?1) layers, if N is a natural number (more than three), and if a cover-layer thickness and intermediate-layer thicknesses are d1, d2, . . . dN, then a difference of 1 ?m or above is set between the sum of di to dj and the sum of dk to dm for arbitrary natural numbers i, j, k, m (i?j?k?m?N). If refractive indexes are different from a standard value or different for each layer, then the thickness of each layer is converted based on a spread width of light according to the thickness.

Abstract: In an optical head device which performs recording or reading of data in/from a high-density optical disc using an objective lens with a large NA, a saw-tooth shape diffraction element is used for also performing recording or reading of data in/from a conventional optical disc, such as DVD, CD, or the like. A step difference that produces an optical path length for blue light which is equal to or longer than the wavelength of the blue light and optical path lengths for red and infrared light which are shorter than the wavelengths of the red and infrared light is utilized so as to exert an inverse action on the blue light to those exerted on the red and infrared light. The effect of increasing the working distances for CD and DVD enables multiple compatibility. The above optical element is integrally combined with the objective lens to perform a tracking servo following operation.

Abstract: Shape-wise thicknesses of a cover layer and first through (N?1)th intermediate layers of an optical recording medium having refractive indexes nr1, nr2 are converted into thicknesses t1, t2 of the respective layers having a predetermined refractive index which makes a divergent amount equal to a divergent amount of a light beam resulting from the thicknesses tr1, tr2, a difference DFF between the sum of a thickness “ti” through a thickness “tj”, and the sum of a thickness “tk” through a thickness “tm” is set to 1 ?m or more (where i, j, k, and m are each any positive integer satisfying i?j<k?m?N), and the thicknesses t1, t2 are calculated by products of a function f(n) expressed by the following formula (1), and the thicknesses tr1, tr2: f(n)=?1.088n3+6.1027n2?12.042n+9.1007 ??(1) in the formula (1), n=nr1, nr2, . . . , and nrN.

Abstract: Provided are an optical head capable of favorably recording or reproducing information to or from an information recording medium including a plurality of information recording surfaces, an optical disc device including the optical head, an information processing device including the optical disc, and an objective lens. The optical head (40) includes a blue-violet laser light source (1) which emits a blue-violet laser beam, an objective lens (8) which has an orbicular zone-shaped diffractive structure, and which diffracts the blue-violet laser beam and converges the generated diffracted light of n-th order (where n is a natural number) on a predetermined information recording surface of a multi-layer optical disc (60), and a light-receiving element (23) which receives the blue-violet laser beam reflected by the predetermined information recording surface, wherein the diffractive structure adds a positive power component and a spherical aberration component to the n-th order diffracted light.

Abstract: Shape-wise thicknesses of a cover layer and first through (N?1)th intermediate layers of an optical recording medium having refractive indexes nr1, nr2 are converted into thicknesses t1, t2 of the respective layers having a predetermined refractive index which makes a divergent amount equal to a divergent amount of a light beam resulting from the thicknesses tr1, tr2, a difference DFF between the sum of a thickness “ti” through a thickness “tj”, and the sum of a thickness “tk” through a thickness “tm” is set to 1 ?m or more (where i, j, k, and m are each any positive integer satisfying i?j<k?m?N), and the thicknesses t1, t2 are calculated by products of a function f(n) expressed by the following formula (1), and the thicknesses tr1, tr2: f(n)=?1.088n3+6.1027n2?12.042n+9.1007 ??(1) in the formula (1), n=nr1, nr2, . . . , and nrN.

Abstract: An objective lens element having improved diffraction efficiency at least one of used wavelengths is provided. The objective lens element includes one surface including: a first region including an optical axis; and a second region surrounding the first region. A periodic first diffraction structure is formed on the first region, and a periodic second diffraction structure different from the first diffraction structure is formed on the second region. The objective lens element satisfies the following conditions. |A1?B1|<|A2?B2|??(1) |B1|?|B2|??(2) Here, A1 and B1 are diffraction orders at the first region to converge light of a first wavelength and light of a second wavelength on a recording surface, respectively, and A2 and B2 are diffraction orders at the second region to converge the light of the first wavelength and the light of the second wavelength on a recording surface, respectively.

Abstract: To provide an optical pickup and an optical information device, capable of obtaining excellent signal characteristics for an optical disk on and/or from which recording and/or reproducing are performed using a laser. The optical pickup includes an optical detector, a support holder for holding the optical detector, and an optical base for fixing the support holder. The support holder has at least two notches at its both ends, the optical base has convex portions corresponding to the notches of the support holder, the optical base and the support holder are fixed by photo-curable adhesives for bonding the convex portions and the support holder to each other, and the shortest distance between the side faces of the convex portions, which do not face each other, is equal to or less than the width of the support holder in the direction of right and left ends.

Abstract: An optical information medium measurement method measures a degree of modulation in an optical information medium of a multilayered structure having a plurality of information layers. The method includes measuring the modulation degree of each layer of the optical information medium, obtaining a thickness between layers of the optical information medium, obtaining a reflectance of each layer of the optical information medium, and converting the modulation degree of each layer. The modulation degree is measured based on a value indicative of the thickness between layers, and a value indicative of the reflectance of each layer.

Abstract: An objective lens, an optical head, an optical disk apparatus and an information processing apparatus which can suppress deterioration of a focal spot caused by a drop in the diffraction efficiency are provided.

Abstract: An optical information medium measurement method, for measuring a degree of modulation in an optical information medium of a multilayered structure having a plurality of information layers, includes a first step of measuring a modulation degree of each layer of the optical information medium, and a second step of obtaining a thickness between layers of the optical information medium. Further, the method includes a third step of obtaining a reflectance of each layer of the optical information medium, and a fourth step of converting the modulation degree of each layer, as measured in the first step, into a modulation degree at a reference optical system differing from the measurement optical system, based on a value indicative of the thickness between layers, the thickness being obtained in the second step, and a value indicative of the reflectance of each layer, as obtained in the third step.

Abstract: An optical head device includes a light blocking region (7y) which is disposed on a light flux of a reflected light beam resulting from reflection by a recording layer on which a blue light beam is focused, and blocks, when there are at least two recording layers on a blue light beam incident side of the recording layer on which the blue light beam is focused or on a side thereof opposite to the blue light beam incident side, reflected light beams resulting from reflection by the at least two recording layers which are incident on a region in a photodetector (9) where the reflected light beams resulting from the reflection by the at least two recording layers interfere with each other. The light blocking region (7y) is not formed on an optical axis of the reflected light beam resulting from the reflection by the recording layer on which the blue light beam is focused. This configuration allows an improvement in the S/N ratio of a signal outputted from the photodetector.

Abstract: An objective lens element which has excellent compatibility with optical discs having different base material thicknesses is provided. An objective lens element 141 has optically functional surfaces on an incident side and an exit side. Either one of the optically functional surfaces is divided into an inner part 131B including a rotational symmetry axis and an outer part 131F which is a ring-shaped region surrounding the inner part 131B. On the inner part 131B, a plurality of discontinuous steps are provided. The plurality of steps change in height in the same direction from the optical axis toward the outer part, and each of the steps causes a constant optical path difference longer than the wavelength ?1 to the first incident light beam 61 and causes a constant optical path difference shorter than the wavelength ?2 to the second incident light beam 62.

Abstract: An objective lens element having excellent compatibility with optical discs having different base material thicknesses is provided. The objective lens element has optically functional surfaces on an incident side and an exit side. At least either one of the optically functional surfaces on the incident side and the exit side includes a diffraction portion which satisfies at least either one of the following formulas (1) and (2): ?1×?2<0 (“×” represents multiplication) ??(1), (sin ?2)/?22=?(sin ?1)/?1 ??(2), where ?1 is the diffraction angle of a light beam having a diffraction order providing the maximum diffraction efficiency at the wavelength ?1, and ?2 is the diffraction angle of a light beam having a diffraction order providing the maximum diffraction efficiency at the wavelength ?2.

Abstract: An optical element which can be shared by three wavelengths for BD, DVD, and CD and which is easily manufactured is provided. An objective lens system includes an optical element 1A and a converging lens element 1B. A first surface of the optical element 1A on an incident side is concentrically divided into a region 11 including a rotational symmetry axis, a region 12, and a region 13. On the optical element 1A, a periodic stair-like diffraction structure and a periodic sawtooth-like diffraction structure are provided. A second surface of the optical element 1A is divided into a region 21 including a rotational symmetry axis, a region 22, and a region 23. On the region 21, a sawtooth-like diffraction structure is provided. The converging lens element 1B converges light having passed through the optical element 1A, to form a spot on an information recording surface of an optical disc.

Abstract: An object of the invention is to provide an optical recording medium and a method for producing an optical recording medium that enable to improve the quality of a servo signal and a reproduction signal. The optical recording medium satisfies: t3?t4?1 ?m, t4?t2?1 ?m, t2?10 ?m, and t1?(t2+t3+t4)?1 ?m, where t1 is a thickness between a surface of the optical recording medium, and the first information recording surface, t2 is a thickness between the first optical recording surface and the second information recording surface, t3 is a thickness between the second optical recording surface and the third information recording surface, and t4 is a thickness between the third optical recording surface and the fourth information recording surface.

Abstract: A small optical pickup of wide spherical aberration correction range includes a rising mirror for perpendicularly deflecting a light beam and guiding the light beam to an objective lens; a spherical aberration correction lens having one surface formed to a larger curvature than the other surface; a lens holder for holding the correction lens so that the surface of large curvature projects towards the rising mirror side; an axially extending guide member; and a slidable part slidable along the guide member. The projecting portion of the slidable part is configured to be fitted within the side surface of the reflecting surface of the rising mirror, and the projecting portion from the lens holder of the spherical aberration correction lens overlaps the reflecting surface of the rising mirror when the spherical aberration correction lens approaches the rising mirror the most.